In recent years FatMax has become quite a buzz word in the world of cycling!
FatMax is the power output where a cyclist's maximal rate of fat oxidation (MFO) occurs.
Training at or around FatMax-intensity will stimulate your fat burning capacity very effectively, and consequently improve your performance on the bike. Simply because an improved capacity to burn fat will spare your carbohydrate stores, leading to enhanced performance in the final hours of a race, where you need the carbs for the last decisive high intensity efforts!
But at which intensity does MFO occur?
A common belief is that MFO typically occurs at an intensity corresponding to 1.7-1.9 mmol lactate. So an intensity just below lactate threshold 1 (LT1), which corresponds to a 2 mmol lactate concentration.
This is also what has been termed 'Zone 2'-training, which is an intensity where the oxidative capacity of the muscle is highly stressed, which leads to improved capacity to use fat as fuel.
If you look at typical training zones (e.g. 5-7 zone model) for cycling, LT1 will typically be in the higher part of the endurance zone (zone 2) or the lower part of the tempo zone (zone 3).
So if you are sticking to these guidelines when trying to boost your fat oxidation you should either:
Train just below a power output that elicits a 2mmol lactate concentration.
Train in the upper part of zone 2 and lower part of zone 3.
But general rules don't apply to everyone, and every cyclist has their own unique metabolic profile including different capabilities to burn fat (depending on training status, gender, acute nutrition and general diet). Hence, the intensity that elicits MFO are vastly different among cyclists!
You can't simply rely on lactate concentrations or training zones to find your FatMax power!
Here is an example.
Last week I looked through data and results from a lab test conducted on a rider I coach.
The rider's FMO (based on stoichiometric data) occurred at an intensity around 150 watts, whereas his LT1 was at 240 watts. The training zones based on his 4 mmol power output (LT2 @ 270 W) came out with a high zone 2-low zone 3 power around 190-210 watts. So basically 3 different intensities for 'FatMax-training'.......
FMO @ 150 W.
LT1 (2mmol lactate) @ 240 W.
High Z2-Low Z3 @ 190-200 W.
In this case the correct and valid FatMax intensity is 150W, which corresponds to a lactate concentration of approximately 1 mmol. Which would happen to be just between this cyclist power zone 1 and zone 2.
So this rider doesn't need to do 'FatMax-intervals' to improve his MFO. He simply just needs to do long slow distance rides at a relative low intensity. Not being said that training at his 2mmol power output or high Z2-lowZ3 won't improve his fat oxidation - it for sure will. But the greatest stimulation of his MFO is at 150 W.
To sum up........
The generalization of FatMax and MFO doesn't apply to every cyclist.
If you want to be sure to know your FatMax power output, you need to do a proper performance test, that will give you a full picture of your metabolic profile - e.g. a lab test or INSCYD PPD Test.
References:
Ed Maunder E, Plews DJ and Kilding AE. Contextualising Maximal Fat Oxidation During Exercise: Determinants and Normative Values. Front. Physiol., 23, 9 (2018).
Ferri Marini, C.; Tadger, P.; Chávez-Guevara, I.A.; Tipton, E.; Meucci, M.; Nikolovski, Z.; Amaro-Gahete, F.J.; Peric, R. Factors Determining the Agreement between Aerobic Threshold and Point of Maximal Fat Oxidation: Follow-Up on a Systematic Review and Meta-Analysis on Association. Int. J. Environ. Res. Public Health 20, 453 (2023).
Purdom, T., Kravitz, L., Dokladny, K. et al. Understanding the factors that effect maximal fat oxidation. J Int Soc Sports Nutr 15, 3 (2018).
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